Regional water availability report Weekly edition 29 June 2020 1 Contents 1. Overview .............................................................................................................................................. 3 2. System risks .......................................................................................................................................... 3 3. Climatic Conditions ............................................................................................................................. 4 4. Southern valley based operational activities ................................................................................... 6 4.1 Murray valley ............................................................................................................................................... 6 4.2 Lower Darling valley ................................................................................................................................... 8 4.3 Murrumbidgee valley ............................................................................................................................... 10 5. Central valley based operational activities .................................................................................... 10 5.1 Lachlan valley ........................................................................................................................................... 13 5.2 Macquarie valley ..................................................................................................................................... 10 6. Northern valley based operational activities ................................................................................. 18 6.1 Namoi valley ............................................................................................................................................. 18 6.2 Gwydir valley ............................................................................................................................................ 20 6.3 Border rivers ............................................................................................................................................... 21 6.4 Barwon-Darling River system ................................................................................................................... 21 7. Coastal valley based operational activities ................................................................................... 27 7.1 Bega river .................................................................................................................................................. 27 7.2 Hunter valley ............................................................................................................................................. 28 7.3 Toonumbar Dam ...................................................................................................................................... 30 8. Rural Dam Levels ............................................................................................................................... 31 Water availability weekly report 2 1. Overview WaterNSW manages and operates 42 dams and storages to deliver water for environmental, domestic, town water, stock, industrial and irrigation purposes across the state. WaterNSW storages provide supplies to all the major river systems in Western NSW, Greater Sydney, the Southern Highlands, Shoalhaven Bay as well as the Hunter, Bega, and Iron Pot valleys in coastal NSW. The total active storage percentage of rural water supplies on 29 June 2020 was 35.0% of the total active storage capacity. This was an increase of 1.3% since last week. The total storage level of urban water supplies on 29 June 2020 was 81.0% of the total storage capacity. A decrease of 0.2% since last week. 2. System risks The relatively small inflows to most northern dams mean that drought measures and works are being reviewed, but most will likely remain in place, despite the larger flows downstream. This is particularly the case for Chaffey, Split Rock and Wyangala Dams, where the risks to critical needs remains high. Risks are also increasing in the Hunter Valley as inflows to Glenbawn and Glennies Ck Dams continue to track well below previous drought records. Water availability weekly report 3 3. Climatic Conditions Figure 1 - Weekly rainfall totals for New South Wales This week’s weather forecast A high pressure system over southeast Australia is slowly tracking to the Tasman Sea as a series of cold fronts approach from the west. The first of these fronts slips to the south on Tuesday. The second front, which is more significant, looks set to cross the state on Thursday. By the weekend a new high pressure system will return over the state. For the coming week negligible rainfall is predicted across parts of the southern region and also north east of the state. The rest of the state is predicted to remain dry Figure 2a – First 4-day Forecast (30 June – 3 July 2020) Figure 2b – Following 4-day forecast (4 – 7 July 2020) Water availability weekly report 4 Climate outlook overview Wetter months likely for late winter to early spring. Issued: 25 June 2020 • The fortnight 29 June to 12 July is likely to be drier than average for most of New South Wales. • August to October is likely to be wetter than average for most of New South Wales (60–75% chance). Figure 3 – 3-month rainfall outlook Water availability weekly report 5 4. 4Southern valley based operational activities 4.1 Murray Valley Storage and release status • Hume Dam is currently 37% of active capacity, and at minimum releases of 600ML/d. • Release downstream of Yarrawonga Weir is at about 10,000ML/day and likely to decrease by 500-1000ML each day, matching the tributary inflows. • Recent rainfall has led to elevated tributary inflows to the River Murray and Lake Victoria is now guaranteed to fill. DPIE-Water declared a period of unregulated flow for certain reaches of the River Murray System starting on the 27 June 2020. • The Edward River Offtake flow is currently about 1,570 ML/d and is likely to remain steady over the week • The Gulpa Creek Offtake flows are at about 200ML/d and likely to increase to about 250ML/d (which is deemed to be the current channel capacity pending remedial works on the Reed bed sills) and then remain steady over the coming week. • Stevens Weir level is about 4.27m and will vary marginally for the next 3-days due to increased flows expected through the forest upstream of Toonalook. Water level upstream of Wakool Canal offtake is about 1.6 m. • Flow downstream of Stevens Weir is about 990 ML/day and is estimated to decrease over the coming week to about 600ML/day. • Flows in the Colligen Creek (380ML/day), Yallakool Creek (240ML/day) are likely to remain relatively steady. Wakool River will have little or no flows due to the lowering of Stevens Weir. • Flow in Niemur River at Mallan School is currently about 43ML/d flow will remain relatively steady around this level while the supplementary event is on. • Merran Creek flows upstream of its confluence with Wakool is about 330 ML/day and is likely to increase to about 350 ML/day over the coming week. With upstream flows continuing to increase from last week's rain. • Flow in Wakool River at Stoney Crossing is currently at about 450 ML/day and is likely to decrease slightly while the supplementary event is on. • Flow at Balranald is currently about 1,040 ML/d and will remain relatively steady over the next week. The end of system target at Balranald for the month of July is 829ML/day. • Lake Victoria is currently holding about 594 GL or 86% of active capacity. The lake is expected to fill over the week. The flow to South Australia is about 3,960 ML/d. Water availability weekly report 6 Environmental water operations • eWater delivery has now ceased into Wakool-Yallakool system and into Colligen-Niemur system. Water availability • The latest Murray Water Allocation Statement 15 May 20 confirmed that general security allocation has increased by 3 per cent. • The allocation announcement for the new water year are expected on 1 July 2020. Drought operation measures • The NSW Murray regulated river water source has remains at Stage 2, meaning drought operational planning has commenced in preparation for extreme dry conditions that may continue through 2020-21. Water quality • Potential Blue Green Algae issues: – Recent Blue Green Algae (BGA) sampling at Lake Hume shows Lake Hume is on a Green alert level. The sites at Heywoods and Ebden indicate Amber alert level. – For more information visit: Water Quality Algae Planned supply interruptions: • Maintenance activities are underway in the Stevens weir gates and super structure under the Coatings Programme. However, the maintenance activity is not expected to impact the normal river operations and Weir levels. Water availability weekly report 7 4.2 Lower Darling valley Storage and release status • Menindee Lakes system collectively holds about 27% of total capacity, and is releasing about 220 ML/d. • The status of individual lakes: Lake Wetherell - 71%, Tandure – 86%, and Lake Pamamaroo – 121%, Copi Hollow – 138%; while Lakes Menindee and Cawndilla remain dry. • As per the Water Sharing Plan, the planned minimum flows for the months of May to October will target 200 ML/day measured at Weir-32. • Water transfer from Lake Wetherell to Lake Pamamaroo has ceased with current levels in Lake Pamamaroo approaching the spill level of the inlet regulator